Directional instrument



7 June 11, 1940 P. KolfLrsMAN 2,203,824

DIRECTIONALI INSTRUMENT Filed Jan. s1, 1940 2. sheets-sheet `1 4i 4 3029223 ae PAUL. KOLLSMAN BY 54m am @d4 ATTORNEY June 1l, 1940. 3 P, KQLLSMAN A V 2,203,824

DIRECTIONAL INSTRUMENT FiledJan. s1, 1940 2`seets-sneet a 93\| |NvENToR FIG. 3 PAUL KOLLSMAN.

BY m

ai ATTORNEY Patented June 11, 194i) UNITED' STATES PATENT AOFFICE Application January 31, 1940, Serial No. 316,683 In Great Britain November 5, 1938 13 Claims.

This invention relates to improvements in directional instruments, more particularly direction indicating instruments for use on craft;

This invention is in part a modification of my V turn indicator described in application Serial No.l

156,550 filed July 30, 1937.

It is an object of this invention to provide'an improved directional instrument capable of maintaining absolute direction with great accuracy I and stability.

It is a further object of this invention to provide a novel directional instrument operating neither on a magnetic nor gyroscopic principle.

The present invention has for its object an i instrument operating on the principle of determining deviation of a flow of fluid from an initial ldirection imparted to said flow. The deviation of the flow of fluid is utilized for determining' a change in absolute direction to which the instru- D ment may be subjected.

It is a further object of this invention to provide, in an instrument of the kind last described, means for biasing the instrument with respect to the magnetic north south direction.

5 From another aspect the invention has for an object to provide a navigating instrument particularly suited forA indicating the direction of flight of a fast moving airplane in which the oscillation of the indicating element in rough air,-

or a northerly turning error, during a turn is eliminated. I

More specifically the invention aims at providing means for directing a flow of fluid' in a predetermined direction vtowards an axis, a rotor ,5 'having surfaces exposed to the said flow whereby upon a turn imparted to the instrument about the said axis the fluid will cause a rotary motion of the rotor which is a multiple of the said turn, and a train of gears for operating indicating means in response to movements of the said rotor, said train of gears having a.' ratio of transmission inverse to the ratio of multiplication by the rotor of the turning movements imparted to the instrument. This "arrangement will cause the L indicating means to maintain absolute direction.

In describing 4and defining the present'invention, the term indicating means" is used to inelude a movable member used for the .purpose of visible indication as well as for the purpose 50 of actuating a relay in an automatic steering device in which case the -movements of the said member may not necessarily be visible. l

'I'he invention thus relates equally to instruments serving as indicators or as a` base line for 55 automatic steering.

(ci. sri-204) Further aims, objects and advantages of this invention will appear from a consideration ofthe description which follows with accompanying drawings showing for purely illustrative. purposes an embodiment of this invention'. It is to be 5 understood, however, that the description is not to be taken in a limiting sense, the scope of this invention being defined in the appended claims.

Referring to the drawings:

Fig. 1 is a vertical cross-section through an vl()4 instrument embodying the present invention;

Fig. 2 is an enlarged vertical cross-section through a modified part of the instrument shown in Fig. l; and' Fig. 3 shows in plan view on an enlarged scale 16 an element of Fig. 2, a section being taken on line 33. A

In Fig. 1, the instrument is shown as compris ing a fluid chamber IIJ oi' preferably toroidal shape formed of a lower part II and an upper part I2 held tightly together and sealed by a gasket I3. The fluid chamber contains a core I4 of toroidal form dividing the chamber I0 into .anupper portion I5 and `a'lower portion I6.

V. 'Ihe chamber I0 may be lled with a charge of 25 uid, preferably liquid, throughpan opening normally closed by a filling screw I1. An expansion chamber shown in the illustrated embodiment as being in the form of a diaphragm capsule I8 may be provided to permit an expansion and contraction of the fluid due to changes in temperature. I

Means are provided for creating a flow of fluid within the chambers I5 and I6. In the illustrated embodiment a centrifugal pump rotor I9 35 is shown having blades 20 and mounted for rotation about a shaft 2l coaxial with the central axis of the toroidal chamber I0.l If the rotor` I9 isiturned about the shaft, it will cause the lluid within the chamber I0 to circulate in the 'direc- 404 tion indicated by arrows 22.

For eliminating turbulence, caused by the rotor, guiding surfaces may be providedl In the illustrated embodiment a first set of guiding surfaces is shown in the upper portion I5 o1 the 45 chamber at 23, a second set being shown in the lower portion I6 of the chamber at 24.

, The fluid leaving the guiding surfaces 24 is free from turbulence and is directed in a direction radial towards the central axis of the chamber. The fluid will converge'at the central axis thence flow along the central axisl and away from said axis to repeat the same circuit. Due to the decreasing cross-sectional area towards the central axis, the rateof flow of the duid is greatly` increasedas the uid particles approach the central axis.

About the central axis there is movable a second rotor 25 having radial vanes 25' acted'upon by the fluid. These vanes make the rotor responsive to changes in theldirection of the flow of fluid.l The rotor 25 is mounted with its shaft 26 in bearings 21 and 28'preferably of the jewel type.

Means are provided for driving the centrifugal pump rotor I9. In the illustrated embodiment a prime mover of the turbine type is shown including a turbine lrotor-29 having vanes or blades 30 at itscircumi'erence to be acted upon by a jet of pressure fluiddirected thereonto from a nozzle 3|. 'I'he turbine rotor has a shaft 32 supported in bearings 33 and 34.

For transmitting power from the prime mover to the centrifugal pump for vcirculating the iiuid, there is shown a magnetic coupling driving the pump rotor I9 through a. liquid-proof thin-Walled portion 35 of the upper part I2 forming the fluid chamber I0. The magnetic coupling comprises a iirst magnetic element 36 secured to the turbine rotor 29 and curved at its ends to form pole pieces 31.'

\ 'I'he second magnetic element or amature 38 is secured to the rotor I9 of the centrifugal pump and is preferably provided with pole pieces 39 at its ends corresponding in shape and number to file pole pieces of the driving magnetic element scribed.

' In the illustrated embodiment an air valve isv shown comprising a plunger operable from a knob 46 through a rod 41. Means may be provided for normally maintaining the valve in an openposition. y

In the illustrated embodiment a helical spring 48 is shown bearing against a shoulder 4%9 in the lindrical portion 45 of the air passage 43 thereby shutting olf the chamber 40 from the pipe coupling 44.

Fluid under pressure is supplied to the driving nozzle by withdrawing air from the chamber 40 through the air passage43`yvhich may be accomplished by connecting a suction pump to the pipe coupling 44. Air of atmospheric pressure will enter the instrument through openings 52 in a' housing 53 in which the elements ofthe instrument are assembled. The housing may be closed at the rear by a cover 54 protecting the. diaphragm capsule I8 and form-ing another chamber 55. .Y

The chamber 55 is in communication with the driving nozzle 3l which is-thus supplied with air at atmospheric pressure., l

Due to the suction pressure existing in the turbine chamber 49 a jet of air vwill issue from the nozzle 34 impinging upon the blades of the turbinerotor to drive the same. The turbine rotor in turn through the magnetic coupling 36 33 drives the centrifugal pump rotor I9."

:acclaim-iv The operation of the device so far described is as follows:-

When a-motion is imparted uponthe instrument about the central axis of the uidvchamber, a tangentiall component is imparted to the fluid particles normally owing in a radial direction towards the rotor 25. Due to the tangential component of movement of the fluid particles.

Vthe rotor 25 is rotated in one direction or the other depending upon the direction of turn imparted to the instrument.

The magnitude of the rotary movement of the rotor 25 depends on the magnitude of the turn imparted to the instrument and is a multiple thereof. In an instrument of the illustrated form, for example, the rotary movement of the rotor 25 will be about six times the turn imparted to the instrument. If, for example, an

airplane on which the illustrated instrument is mounted makes a turn of 30, the rotor 25 will amplify this t'urn andl will make a rotary motion of six times 309, that is- 180.

This amplified movement may be reduced again' and thereby utilized for maintaining a' movable member fixed with respect to absolute `direction, that is fixed in azimuth in the` illus ment, the turn will be multiplied by the rotor 25 and the multiplied motion again -reduced by the train of gears 56, 51 so as to maintain the gear 51 'fixed in space. The gear 51 may thus-be used 4for operating a .visible indicator or' the movable member of a control relay in an automatic steering device. f I' In the'ilustrated embodiment cator is shown comprising a dial 6I mounted in the front flange 62 of the housing 53 and a pointer 63 movablev relatively to the dial. 'I'he pointer is carried by a shaft 64 supported in bearings 65 and 66, the latter bearing being formed in a bracket 61 extending from a tubular member 63 in the housing 53.

' For rotating the pointer shaft 64 in respo to the movement of the housing 53 relativelyto the gear 51 maintaining absolute direction, a

bevel gear train is shown. A first bevel gear 63 is carried by the pointer shaft and meshes with a second bevel gear" 10 mounted on a vshaft 1I movable in vertical bearings 12 and 13. T'he vertical shaft 1I may be directly connected to the gear 51.

' In the illustrated embodiment, however. a magnetic coupling is shown comprislngda first magnetic element 14 on the shaft 58 in the'uid chamber I 0 and a vsecond magnetic element 15 `on the shaft outsuigf of the said fluid chamber. The magneticl elements 14 and 15 are. preferably made of equal pole strength as to'make the ,magnetic coupling neutral with respect to the surrounding parts.

An indication oi' absolute direction is thus accomplished in the following manner: I

As hereinbeforeA described, the gear 51 will remain xed in azimuth. Accordingly, the shaft.

-a visible indi- 2,203,824' which the instrument is mounted makes a turn.`

the turn is imparted to the instrument housing 53, which thus turns relatively to the shaft 1| and the bevel gear 10 mounted thereon, the bevel `gear 69 will thus be caused to roll on the bevel gear 10 turning the pointer and indicating the amount of deviation from the initial direction.

In the illustrated embodiment, the instrument housing is closed at the front by means of a front ring 16 carrying a cover glass 11. The front ring 19 maybe provided with a panel bead 13 to fit into an instrument panel 19.

With the structure thus far described, the instrument is capableof indicating absolute directions with suflicient accuracy over a substantial period of time. After a long period of time, however, during which the instrument was subjected to various turning movements, the gear 51 may deviate slightly from its initial position thus causing the pointer 93 to deviate also.

In this respectthe instrument is comparable `to a directional gyroscope which after being set in an initial position willmaintain that position over a certain period of time after which the gyroscopev and the indicator operated thereby will show a noticeable deviation from the initial position.

To correct .this deviation resetting means may 'be employed or means may be provided for biasing the direction maintaining element towards a predetermined direction. The reference direction may be the direction of the earths magnetic field. Accordingly, a magnetic compass element may be employed for biasing the directional instrument. Y

It is preferable to make the influence of a biasing element small as to become effective only over a substantial period of time to avoid errors from being introduced should the biasing element temporarily deviate from its properposition.

In the illustrated embodiment, a directional magnet 8l is shown enclosed in a float 0| provided with damping fins 92. The magnet, the float and the ,damping fins constitute a movable unit which, in the illustrated embodiment, is supported slightly above its center of gravity in a point 891m a cup shaped-.bearing 9'4 for movement in azimuthaand freedom to tilt relatively to 9| and an expansion chamber shown in the form the vertical axis.

The bearing 94 is mounted ina stem w85 slideable in a. sleeve 86" mounted in a compass bowl 81 coaxially with the shaft 1|. A spring 90 may be provided between the cup shaped portion 90 of the stem anda shoulder 89 on the sleeve. The compass bowl may be illled with a charge of liquid oi a diaphragm capsule 92 may be provided to permit of expansion and contraction of the liquid 9| in response to changes in temperature.

The magnetic element is coupled with the direction maintaining shaft or element of the turn zus responsive instrument. In Vthe illustrated embodiment a resilient coupling is provided includ- /ing two follower magnets mounted to either side of the shaft 1|, one of the magnets being visible in the drawing at 93. The magnetic coupling thus constituted by thel follower magnets 93 and the directional magnet 90 may assume the form ff, disclosed in my application No. 217,904 `flied July `'1o The controlling or -biasing influence of the magnetic element on the shaft 1| is relatively weak.

iniluen'c o n the shaft 1| and the indicator during theshort time of disturbance.

Over a long period of time, however, during which the magnetic element is in its proper north south position, it will exert a torque on the shaft 1| should the said shaft have deviated from its correct position in azimuth lthereby `correcting the initial position of the instrument.

An almostJ instantaneous resetting of the instrument with respect to the magnetic northl south position may be accomplished by Irendering the. iluid operated direction maintaining part of the device inoperative during the time of resetting. This may be done by closing` the valve l 45, by pressing Ithe knob 48.

The turbine rotor29 will thus be deprived of its driving power and the circulation of the fluid within the chamber l0 will cease. The direction maintaining action of therotor 25- thus being suspended, the magnetic element 80 willv quickly, m

through the resilient couplings 80, 93 and. 14, 15, turn the rotor 25 into the correct initial position.

If the knob 46 is released, the turbine rotor will again be supplied with driving energy and the iiuid operated part of the instrument will resume its operation in the hereinbefore described manner.

The controlling torque of the magnetic directional element may be modified as to be relatively strong while 'the magnetic directional element is in its proper north south position, and as to be weak if the magnetic element deviates from its proper position. A torque limiting and biasing coupling may thus be employed between the magnetic element and, the indicator, or the iiuid operated part of the instrument respectively.

` In Figs. 2 and-3, a modification of the instrument of Fig. 1 is shown including a torque limiting and biasing coupling of the type disclosed and claimed in -my izo-pending application, Serial No. 316,684, filed Jan. 31, 1940.

A movable frame 94 is substituted for the shaft 1| Vof Fig. 1, the frame having a shaft extension 96 for resting in bearings 12 and 13 of the housing 00, To the extension 95'there is secured the bevel gear 10 'meshing""with the gear 69 of lthe arm extension' 99 at |02 bearing a roller |03 at one end and a stud |04 at the other. The free end o f a spring |05 bears against the st-ud |04, the spring being secured to thearm extension |00 at |06;

' To balance for the mass carried by arm extension 99, a counterweight |01 may be mounted to the arm 99' to counterbalance the mass carriedby arm extension 99.

The roller |03 movable with the support bears against the circumference of a cam |98 secured to the frame 94 at |09 and ||0. Themcam |08 may be heart-shaped and is shown' eccentrically arranged as will appear from Fig.A 3 as to cause the spring urged roller |03 to .move into a position closest to the axis of the shaft 95.

The torque limiting and biasing coupling thus comprises two' members movable relatively to each other, either one'of which. may be regarded as the driving or the driven element. The coupling `is biasing in that the spring urged roller always tends to move into a predetermined position on the cam thereby aligning the driving and the driven member, in the illustrated embodiment, the support and the frame.

'The coupling is also torque limiting as the roller will offer considerable resistance to its becoming displaced out of the indentation of the cam, the portion closest the central axis. The ca m is preferably so shaped that for small displacements, the roller will move .the bell crank lever a substantial amount about its pivot Il! against the action of the spring.

`Thus the torque exerted by one of the members of the'torque limiting and biasing coupling `upon the other is considerable for small displacements of the roller out of the indentation in the neighborhood of which the cam is st eep. In portions opposite the indentation, the cam is relatively flatthus causing only a small pivotal movement of the bell crank lever Illl per degree of relative movement between the elements of the coupling.

'Ihe operation of the torque limiting andkbiasing coupling in connection with the instrument hereinbefore described i's as follows:

'I'he biasing torque exerted on the uid operated part of the instrument is relatively strong while the directional magnetic element is in its proper north south position. If, however, during a turn or a steep banking of the plane, the magnetic element is caused to deviate, the roller of 'the coupling will move out of the indentation onto the iiat portionof-the cam exerting only a vvery small torque upon the fluid operated part of the instrument.

The uid operated part will thus prevent the pointer from. being deviated from its correct position even during periods in which' the position of the turbed.

Obviously the present invention is not restricted. toV the particular embodiments herein shown and described. Moreover, it is not indispensable that all the features of the invention be used conjointly as they may advantageously be employed in various combinations and sub-combinations.

What is claimed is:

1. A direction indicating instrument for craft comprising, in combination, means fordirecting a yflow of fluid in a predetermined direction towards, and converging from all sides at, an axis; arotor mounted for rotation about said axis relatively to said flow directing means. said rotor -having surfaces exposed to said flow `whereby upon a turn imparted to said instrument about said axis said flow will be deflected from said predetermined direction imparting to said rotor a motion which is a multiple of said turn; indicating means; and a train of gears connecting said indicating means and said rotor, the ratio oftransmission ofthe gear train being inverse to the ratio of multiplication by said rotor of vto said ilow directing n'ieans, said rotor having radial surfaces exposedv to said iiow, whereby vmagnetic compass element is disupon a turn imparted to said instrument about said axis said flow will be deflected from saidl predetermined direction imparting to said rotor a motion which isa multiple of said turn; indicating means; and a train of gears connecting lsaid indicating means and saidrotor, the ratio vof transmission of the gear train being inverse to the ratio of multiplication by said rotor of the turning movements imparted to the instrument, whereby said indicating means will indicate absolute direction.

3. A direction indicating instrument for craft comprising; in combination, a casing providing a hollow chamber and having a core therein of substantially toroidal form having a central axis;

.a charge of'iiuid in said casing; means for circulating said fluid within said chamber about said core in a path substantially radially towards said lparted to said casing about said axis, thexrotation of said rotor being a multiple of the rota- 4 tion imparted to said casing; indicating means;

4and a train of gears connecting said indicating meansl and said rotor, the ratio of transmission of the gear train being inverse to the ratio of multiplication 'by said rotor of the turning movements imparted to the instrument, whereby said indicating means will indicate absolute direction.

'4. A direction indicating instrument for craft comprising, in combination, a closed toroidal fluid chamberl having a central axis; a toroidal core mounted coaxially therein; a charge of liquid illling the-space between Vsaid core and chamber; a first rotor within said chamber forcirculating said charge of liquid about said core in a path substantially radially towards said central axis to converge at said axis, iiow along saidaxis, and then' away from said axis to repeat the same circuit; an armature carried by said rst rotor; a driving magnetic element mounted outside said chamber and coaxial with saidj rst rotor acting on said armature; a prime mover connected to said magnetic element; a second rotor having radial vanes mounted within said chamber for rotation about .said axis; guiding surfaces flxedly mounted within said chamber directing the converging liquid onto the vanes of said second rotor; indicating means outside said chamber; and actuating means for actuating through the wall of said chamber said indicating means in response to movements of said j rotor which are a multiple of a rotary motion imparted to said chamber, said actuating means including a magnetic coupling comprising a rst and second magnetic element inside and outside the said chamber, respectively, and a gear train the ratio of transmission of which is inverse to the amount of multiplication by said second rotor of a turning movement imparted to said chamber. Y

5. A directional instrument for craft comprising, in combination, means for directing a flow of uid in a predetermined direction towards, and converging from all sides at, an axis; a rotor mounted for rotation about said axis relatively to said ow directing means, said rotor having surfaces exposed to said iiow whereby upon a turn imparted to said `instrument about said axis said flow will be deflected from said predetermined 6. A directional instrument for craft comprising, in combination, means for directing a fiow` of fluid in a predetermined direction towards. and converging from all sides'at, an axis; a rotor mounted for rotation about said axis relatively to said flow directing means, said rotor having surfaces exposed to said flow whereby upon a turn rotor; a driving magnetic element mounted outside said chamber and coaxial with said first rotor acting on said armature; a prime mover.

connected to said magnetic. element; a second rotor having radialvanes mounted within said chamber for rotation about said axis; guiding surfaces xedly mounted vwithin said chamber` directing the converging liquid onto the vanes of said second rotor; a first vertical shaft mounted inside said chamber; a train of gears connecting said second rotor and said vertical shaft, the ratio of transmission being inverse to the amount of multiplication by said second rotor ofI a turning movement imparted to said chamber; a

second vertical shaft mounted coaxial with said first shaft outside of said chamber; magnetic imparted to said instrument about said axis said flow will be deflected from said predetermined direction imparting to said rotor a motion which i is a multiple of said turn; a member rotatable about a vertical axis; a train of gears connecting said rotatable member and said rotor, the ratio` of transmission of the gear train being inverse to the ratio of Vmultiplication by said rotor of the turning movements imparted to said instru ment; a directional compass magnet mounted coaxially with said rotatable member; and a Afollower magnet connected to said member coupling said member to said compass magnet.

'7. A direction indicating instrument for craft comprising, in combination, a closed toroidal fluid chamber havingl a central axis; .a torcidal core mounted coaxially therein; a charge of liquid filling the space between said core andchamber;

a rst rotor within said chamber for circuatingV said charge o f liquid about said core in a path"l substantially radially towards said central axis to converge at said axis, now along said axis, and then away from said axis to repeat the same circuit; an armature carried by said first rotor;.a

`lili driving magnetic element mounted outside said chamber and coaxial with said first rotor acting on said armature; a prime vmover connected to said magnetic element; a second rotor having t radial vanes mounted within said chamber for rotation about said axis; guiding surfaces fixedly y mounted Within said chamber directingthe converging liquid onto the vanes of said second rotor; a first vertical shaft mounted inside lsaid chamber; a train of gears connecting said second rotor and said vertical shaft, the ratio of transmission being inverse to the amount of multiplication bysaid second rotor of a turning move- 'ment imparted to said chamber; a second vertical shaft mounted coaxial with said first shaft outside of said chamber; magnetic coupling'means for connecting said rst and-second shaft; a

directional compass magnet mounted coaxially` with said second shaft and coupled therewith; and indicating means connected to be operated from said second shaft.

8. A direction indicating instrument for craft comprising, in'combwination, a closed toroidal fluid chamber having a central axis; a toroidal core mounted coaxially therein; a charge, of liquid filling the space between said core and chamber; a first rotor within said chamber for circulating said charge of liquid about said core i in a path substantially radially towards said central axis' to converge at said axis, flow along said s axis; and then away from said axis to repeat the same circuit; an armature carried by said first coupling means for connecting said first and second shaft; a directional compass magnet mounted coaxially with said second shaft; resilient coupling means connecting said compass magnetand said second shaft; and indicating means connected to said second shaft, said indicating means including a vertical dial.

9. A direction indicating instrument for craft comprising, in combination, means for directing a flow of fluidin apredete'rmineddirection towards, and converging from all sides at, an axisjA a rotor `mounted for rotation about said axis `relatively'to said flow directing means, said rotor having surfaces exposed to said flowwhereby '3o upon a turn imparted to said instrument-about said axis said flow will be'deflected from said 1 predetermined direction imparting to said rotor a motion which is a multiple of said turn; a rotatable shaft; a train of gears connecting said shaft and said rotor, the ratio of transmission of the gear train being inverse to the ratio of multiplication by said rotor of the turning movements imparted tothe instrument; a directional compass magnet; and indicating means resiliently coupled to both the compass magnet and said shaft.

10. A direction indicating instrument for craft comprising, in combination, means for directing a flow of fluid in a predetermined direction towards, and converging from all sides at, an axis; a rotor mounted for rotation about said axis relatively to said flow directing means, said rotor having surfaces exposed to said flow whereby upon a turn imparted to said instrument about said axis said flow will be deected from said predetermined direction imparting to said rotor a motion/which is a multiple of said'turn; a

rotatable shaft; attain of gears connecting said shaft and said rotor, the ratio of transmission of the gear train being inverse to the ratio'of multiplication by said rotor of the turning movements imparted to the instrument; a directional compass magnet; a torque limiting and biasing coupling connecting said magnet and said rotatable shaft, said coupling including a rst and a second rotatable member, a. heart shaped cam on said first rotatable member, a roller on said second member anda spring urging said roller against said cam; and .indicating means conr nected to be actuated from one of said members.

, 11e. A direction indicating instrument for craft comprising-in combination, means for directing a ilowof uid in a predetermined direction towards, and converging from all sides at, an axis; a rotor mounted for rotation about said axis rela- 4'tively tosaid flowdirecting means, said rotor having surfaces exposed to said flow whereby upon a turn imparted to said instrument about said axis said now will be deected from said predetermined direction imparting'to said rotor a motion which is a multiple'of said turn; a rotatable shaft; a train of gears connecting said shaft and said rotor, the ratio of transmission of the gear train being inverse to the ratio of multiplication by said rotor of the turning movements imparted to the instrument; a directional coml pass magnet mounted coaxially with said rotatauid chamber having a central axis; a toroidlal core mounted coaxially therein; a charge of liquid filling the space between said core and chamber;

a first rotor within said chamber for circulating said charge of liquid about said core in a Vpath substantially radially towards said central axis to converge.at said axis, flow along said axis,

' and then away from said axis to repeat the same circuit; an armature carried by said first rotor; a driving magnetic element mounted outside said chamber and coaxial with s aid first rotor acting on said armature; a prime mover connected to saidmagnetic element; a; second rotor having radial vanes mounted within `said chamber vfor rotation about said axis; guiding surfaces iixedly mounted within said chamber directing the converging liquid onto the vanes of said second rotor; afirst vertical shaft mounted inside said chamber a train of gears connecting said second rotor and said vertical shaft, the ratio of transmission being inverse to the amount of multiplication by said second rotor of va turning movement imparted to said chamber; a second vertical shait` mounted coaxial with said first shaft outside-ibi said chamber; magnetic coupling means for co `neting said ilrst and second shaft; a directional;-

compass magnet mounted coaxially with said second shaft and coupled therewith; indicating means connected to be operatedfrom said second shaft; and manually operable control means for dal iiuid chamber having a central axis; a tor' oidal core mounted coaxially therein; a charge of liquid filling the space between said core and chamber; a rst rotor within said chamber for circulating said charge of liquid about said core in a path substantially radially towards said central axis to converge at said axis, iiow along said axis, and then away from said axis to repeat the same circuit; an armature carriedtby said first rotor; a driving magnetic element mounted outside said chamber and coaxial with said first rotor acting on said armature; a prime mover connected to said magnetic element; a second rotor having radial vanes mounted within said chamber for rotation about said axis; guiding surfaces iixedly mounted within said chamber directing theconverging liquid onto the vanes of said second rotor; afirst vertical shaft mounted inside said chamber; a train of gears connecting said second rotor and said vertical shaft, the ratio of transmission being inverse to the amount of multiplication by said second rotor ofv a turning movement imparted to said chamber; a second vertical shaft mounted coaxial with said `iirst shaft outside of said chamber; magnetic coupling means for connecting said first and second shaft; a directional compass magnet mounted coaxially with said second shaft; resilient coupling means connecting said compass magnet and said second shaft; indicating means connected to said second shaft, said indicating means including a vertical dial; and manually operable control means for temporarily rendering said prime mover inoperative, whereby the instument will be quickly reset with respect to the "magnetic north south direction.

PAUL KOLLSMAN. 

